The embodiments described herein relate to magnetic resonance imaging (MRI) apparatuses and in particular to a magnetic resonance imaging apparatus that detects biological movement of a subject in imaging.
Various methods have been conventionally proposed for reducing biological movement artifacts in a generated image in imaging by a magnetic resonance imaging apparatus. In a method, for example, the following processing is carried out: the position of such a region of interest as a diaphragm moving with biological movement under normal aspiration is detected; an excited section of the subject is corrected in real time in accordance with change of the position of the region of interest; and an MR (Magnetic Resonance) signal is thereby constantly acquired from the identical section. In another method, for example, the following processing is carried out: the position of such a region of interest as a diaphragm is detected; and an imaging sequence is changed or imaging data used for image generation is selected based on the detected position. (Refer to Paragraph 0047 to Paragraph 0055 of Japanese Unexamined Patent Publication No. 2007-111188, and Paragraph 0057 to Paragraph 0062 of Japanese Unexamined Patent Publication No. 2007-098026, for example.)
An example of methods for detecting the position of such a region of interest as a diaphragm is such that: a navigator area embracing that region of interest is excited to acquire an MR signal generated from this area; an intensity profile indicating the relation between a position in the navigator area and the intensity of that signal is generated; and an edge is detected in that intensity profile using a differentiation, the Du method (Refer to JOURNAL OF CARDIOVASCULAR MAGNETICRESONANCE, Vol. 6, No. 2, pp. 483-490, 2004, for example), or the like.
There is known the following method for favorably acquiring an MR signal generated in a navigator area or an imaging area: an RF coil (Radio-Frequency coil), such as a phased-array coil, having multiple coil elements is placed in proximity to a subject and an MR signal is received by this RF coil.
However, an MR signal from a navigator area received at each coil element is varied according to the positional relation between the region of interest of the subject included in the navigator area and the coil element. For this reason, if a subject or an RF coil is changed or the arrangement of an RF coil is changed, the following may take place: the most appropriate coil element that receives an MR signal with which the position of the region of interest can be most stably detected may be changed. Therefore, it is difficult to stably detect biological movement of the subject.